This invention relates in general to the construction of devices for closing off fluid flows and in particular to a new and useful device for preventing damage of a closing valve member which is moved rapidly into engagement with a closing seat by construction which includes a bolster stop face which is engaged by a moving part driving the closing member to stop the movement thereof and to thereafter deform and absorb the shock of rapid stopping.
The subject matter of the invention is an explosion barring shutoff device including a working-fluid-operated shutting member, of the kind used as safety devices in pipe lines for conducting fluid media (gases, liquids, dusts) which, under certain operating conditions, tend to explode. Such a shutoff device (gate or disc) is responsive to a flame alarm provided upstream of the device and is intended to shut off the conduit within a time so short as to prevent a propagation of the explosion beyond the shutting member. It is known to close gate members of this kind by means of suitable working fluid, for example nitrogen or air, and closing times of 40 to 50 milliseconds have been achieved. Depending on the inflammability of the medium or the speed of propagation of the explosion, the flame alarm must be provided relatively far in advance of the gate, which means that relatively long sections of the pipe line remain unprotected. Shorter shut-off times may help. However, since such devices ordinarily comprise relatively large closing plates or discs, and thus a big mass to be moved, not only correspondingly high working-fluid pressures are needed to obtain the necessary short closing time, but also impact forces of such power are produced that the shutting member and its seats, or the provided seals, may easily be destroyed, and the entire housing for the shutting member must be made sufficiently massive and resistant, at considerably high expense.
The present invention is directed to a shutoff device for cutting off the flow of fluid media making it possible with a minimum of expenses to obtain far shorter closing times as compared to the equivalent prior art devices and causing no destruction of component parts which would affect the further shutoff function.
The invention relates particularly to an explosion barring shutoff device with a working-fluid-operated shutting member. The actuating member which transmits the closing force of the working fluid to the shutting member is coupled to the shutting member and the coupling is designed as a stop, cooperative during the final fraction of the closing stroke of the shutting member, with a bolster. The bolster is supported on the housing of the device and is made of non-elastic material capable of permanent plastic deformation and it is deformed by the stop during the final fraction of the closing stroke of the closing member while absorbing the impact energy of the shutting member.
Lead has proved particularly advantageous as the bolster material. Taking into account the stop faces, the moved mass of the closing member, and the driving force, the mass and thickness of the bolster (in the direction of motion of the closing member) can be determined to the effect that following the impact of the stop on the bolster and upon a correspondingly non-elastic deformation of the latter, the shutting member stops exactly in the closing position. Because of the completely non-elastic deformation of the bolster, no forces are produced, neither in the housing supporting the bolster nor in the coupling member or the closing member, which would cause destructive shocks. Experience has shown that with a proper arrangement alone of the stop and the bolster in accordance with the invention, thus without a special reinforcement of the component parts of the device, even conventional gates or discs which are not intended as safety members, may be adapted to provide a perfectly operating explosion-proof shutoff device which can repeatedly perform its closing function, merely upon exchanging the deformed bolster.
Accordingly, it is an object of the invention to provide in a shutoff device which comprises a housing having a closable flow passage, a recessed seat to which a valve closing plate member is movable to a closed position from an open position spaced from the seat and which also includes a fluid-operated piston or similar device which is connected to the closing plate to move it to the closed position, the improvement which comprises a stop defined between the connection of the piston to the closing member in the housing which includes a stop face movable with the piston and the closing member and a stop bolster made of a non-elastic deformable material disposed to engage the stop and interrupt the movement of the piston immediately before the closing member engages on the seat and wherein the bolster member is deformable to permit further closing movement of the closing member into engagement with the seat upon the plastic deformation of the bolster which absorbs the impact of the stopping.
A further object of the invention is to provide an arrangement for stopping the instantaneous movement of a closing device permitting subsequent further closing movement and absorbtion of a shock of the interrupting of the movement.
A further object of the invention is to provide a fluid flow control device which operates substantially without shock which is simple in design, rugged in construction and economical to manufacture.
The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of this disclosure. For a better understanding of the invention, its operating advantages and specific objects attained by its uses, reference is made to the accompanying drawings and descriptive matter in which preferred embodiments of the invention are illustrated.